For my book I've done research into a lot of subjects, including 1920's slang. People in the 20's, like people of every time period, had their own unique way of making themselves understood. "Horesefeathers!" they might say, or "None of your beeswax!" "That's the cat's pajamas!"

Fast forward to the 2000's. (The Aughts? The Zips? How did we let this decade slip by without giving it a decent name?) Most of this language has now been downgraded to cutesy, juvenile slang. Problem is, my characters aren't supposed to sound cutesy and juvenile when they say it. They're, like, for serious.

So: opinions? Can the 20's slang, or stick it only in the mouths of characters who can reasonably be a little bit cute? Any ideas?